1. Field of the Invention
This invention relates to a method and an apparatus for dressing an electroplated grinding wheel in which abrasive grains are held on the peripheral surface of a circular core.
2. Prior Art of the Invention
FIG. 1 shows a well known electroplated grinding wheel. Diamond grains or CBN (Cubic Boron Nitride) grains 14 are held on the peripheral surface of a circular core 12 by a nickel plating layer 13. When the change in height among the abrasive grains 14 is large, the surface roughness of the grinding wheel becomes worse, deteriorating the surface roughness of the finished surface of a workpiece ground by the grinding wheel.
To improve the surface roughness of the finished surface of a workpiece, a method has been proposed in which an electroplated grinding wheel is trued with a diamond truing wheel. By this truing, the top portions of some abrasive grains whose heights are relatively high are removed so that flat surfaces 14a are formed at their tops, as shown in FIG. 2. This method, however, has a problem that the grinding resistance during grinding operations is very high just after the truing, because the tops of some abrasive grains are flat. The high grinding resistance causes a rapid wear of the abrasive grains and other problems.
In another method, abrasive grains having the same diameter are used so as to reduce the change in height among the abrasive grains. This method, however, has a problem that a large amount of time and labor cost are required for selecting abrasive grains having the same diameter, thereby resulting in an increase of the production cost.